package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

/**
 * 封装redis工具类
 */
@Slf4j
@Component
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }
    public void set(String key, Object value, Long time, TimeUnit unit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    /**
     * 设置逻辑过期
     * @param key
     * @param value
     * @param time
     * @param unit
     */
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit) {
        //设置逻辑过期
        RedisData redisData= new RedisData();
        redisData.setData(value);
        //逻辑过期时间
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    /**
     * * 根据id查询店铺，并且添加缓存,缓存穿透
     * @param id
     * @return
     */
    public <R,ID>R queryWithPassTrough(
            String keyPrefix, ID id , Class<R> type, Function<ID,R> dbFallback, Long time, TimeUnit unit)  {
        String key=keyPrefix+id;
        //1.从redis查询商铺缓存,对象用hash
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(json)) {
            //3.存在，直接返回,转换为java对象
            return JSONUtil.toBean(json, type);
        }
        //判断是否是空值
        if (json !=null) {
            //返回错误信息
            return null;
        }
        //4.不存在，使用者来查询数据库
        R r = dbFallback.apply(id);
        //5.不存在，返回错误
        if (r == null) {
            //防止缓存透，将控制写入redis
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL , TimeUnit.MINUTES);
            //返回错误信息
           return null;
        }
        //6.存在，写入redis
        this.set(key, r, time, unit);
        //7.返回
        return r;
    }


    //创建线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR= Executors.newScheduledThreadPool(10);

    //防止击穿
    public <R,ID> R queryWithLogicalExpire(String keyPrefix,ID id,Class<R> type,Function<ID,R> dbFallback,Long time,TimeUnit unit)  {
        String key=keyPrefix+id;
        //1.从redis查询商铺缓存,对象用hash
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(json)) {
            //3.存在，直接返回null
            return null;

        }
        //4.命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        //获取店铺但是是json格式
        JSONObject data = (JSONObject) redisData.getData();
        //获取shop
        R r = JSONUtil.toBean(data, type);
        //获取过期时间
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1未过期，直接返回店铺信息
            return r;
        }
        //5.2.已过期，需要缓存重建
        //6.缓存重建
        //6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean flag = tryLock(lockKey);
        //6.2判断是否获取锁
        if (flag) {
            //6.3成功，开启独立线程实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //重建缓存
                    //查询数据库
                      R r1 = dbFallback.apply(id);
                    //写入redis
                      this.setWithLogicalExpire(key, r1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unLock(lockKey);
                }

            });
        }
        //6.4失败，返回过期商品信息
        return r;
    }
    //获取互斥锁
    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        //使用工具类返回
        return BooleanUtil.isTrue(flag);
    }

    //释放互斥锁
    private void unLock(String key) {
        stringRedisTemplate.delete(key);
    }




}
